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MS-DOS
MS-DOS (short for 'M'icro's'''oft '''D'isk 'O'perating 'S'ystem) was an operating system commercialised by Microsoft. It was the most commonly used member of the DOS family of operating systems, and was the dominant operating system for the PC-compatible platform during the 1980s. It has gradually been replaced on consumer desktop computers by various generations of the Windows operating system. MS-DOS was originally released in 1981 and had eight major versions released before Microsoft stopped development in 2000. It was the key product in Microsoft's growth from a programming languages company to a diverse software development firm, providing the company with essential revenue and marketing resources. It also provided the platform on which early versions of Windows ran. Competition On the IBM PC (and clones) platform, the initial competition to the PC-DOS/MS-DOS line came from Digital Research, whose CP/M operating system had inspired MS-DOS. Digital Research developed CP/M-86 and offered it to computer manufacturers as an alternate to MS-DOS and Microsoft's licensing requirements. In the business world, the PC platform that MS-DOS was tied to faced competition from the Unix operating system, which ran on many different hardware architectures. Microsoft even sold a version of Unix called Xenix. In the emerging world of home users, a variety of other hardware platforms were in serious competition with the IBM PC: the Apple II, the early Apple Macintosh, the Commodore 64 and others. At first, the competition for these other platforms was with IBM PC computers running MS-DOS. With the advent of IBM PC clones all running on Intel processors, the name IBM became less important to home users. What was important was keeping up with Intel's steadily increasing clock speeds and the ability to run MS-DOS. Microsoft and IBM together began what was intended as the follow-on to DOS, called OS/2. When OS/2 was released in 1987, Microsoft began an advertising campaign announcing that "DOS is Dead", boldly proclaiming version 4 was the last full release. MS-DOS had grown in spurts, with many significant features being taken (or duplicated) from other products and operating systems, as well as reverse-engineering tools and utilities including Norton Utilities, PC Tools (Microsoft Anti-Virus), QEMM expanded memory manager, DOS/4GW (a 32-bit DOS extender), Stacker disk compression, and so on. OS/2 offered a number of advanced features that had been written together, and was seen as the legitimate heir to the "kludgy" DOS platform. Digital Research, recognizing the need to continue the lower-level platform represented by DOS, then developed DR-DOS 5, which mirrored the OS/2 "platform integration" model by adding features that were available only as third-party add-ons for MS-DOS. Unwilling to lose any portion of the market, Microsoft responded by announcing the "pending" release of MS-DOS 5.0 in May 1990. This effectively killed most of DR-DOS' sales, until the actual release of MS-DOS 5.0 in June 1991. Digital Research brought out DR-DOS 6, which sold well until the "pre-announcement" of MS-DOS 6.0 again stifled the sales of DR-DOS. Microsoft has been accused of carefully orchestrating leaks about future versions of MS-DOS in an attempt to create what in the industry is called FUD (fear, uncertainty and doubt) regarding DR-DOS. For example, in October 1990, shortly after the release of DR DOS 5.0, and long before the eventual June 1991 release of MS-DOS 5.0, stories on feature enhancements in MS-DOS started to appear in InfoWorld and PC Week. Brad Silverberg, Vice President of Systems Software at Microsoft and General Manager of its Windows and MS-DOS Business Unit, wrote a forceful letter to PC Week (November 5, 1990), denying that Microsoft was engaged in FUD tactics ("to serve our customers better, we decided to be more forthcoming about version 5.0") and denying that Microsoft copies features from DR-DOS: "The feature enhancements of MS-DOS version 5.0 were decided and development was begun long before we heard about DR-DOS 5.0. There will be some similar features. With 50 million MS-DOS users, it shouldn't be surprising that DRI has heard some of the same requests from customers that we have." — (Schulman et al. 1994). The pact between Microsoft and IBM to promote OS/2 began to fall apart in 1990 when Windows 3.0 became a marketplace success. Much of Microsoft's further contributions to OS/2 also went in to creating a third GUI replacement for DOS, Windows NT 4.0. IBM, which had already been developing the next version of OS/2, carried on development of the platform without Microsoft and sold it as the alternative to DOS and Windows. End of MS-DOS MS-DOS has effectively ceased to exist as a platform for desktop computing. Since the releases of Windows 9x, it was integrated as a full product mostly used for bootstrapping, and no longer officially released as a standalone DOS. It was still available, but became increasingly irrelevant as development shifted to the Windows API. Windows XP contains a copy of the core MS-DOS 8.0 files from Windows Me, accessible only by formatting a floppy as an "MS-DOS startup disk". Attempting to run COMMAND.COM from such a disk under the NTVDM results in the message "Incorrect MS-DOS version". With Windows Vista the files on the startup disk are dated April 18, 2005 but are otherwise unchanged, including the string "MS-DOS Version 8 © Copyright 1981-1999 Microsoft Corp" inside COMMAND.COM. Today, DOS is still used in embedded x86 systems due to its simple architecture, and minimal memory and processor requirements. The command line interpreter of Windows NT 4.0, CMD.EXE, maintains most of the same commands and some compatibility with DOS batch files. Legal issues As a response to Digital Research's DR-DOS 6.0, which bundled "SuperStor" disk compression, Microsoft opened negotiations with Stac Electronics, vendor of the most popular DOS disk compression tool, Stacker. In the due diligence process, Stac engineers had shown Microsoft some Stacker source code. Stac was unwilling to meet Microsoft's terms for licensing Stacker and withdrew from the negotiations. Microsoft chose to license Vertisoft's DoubleDisk software, using its code as the core for its DoubleSpace disk compression. MS-DOS 6.0 and 6.20 were released in 1993, both including the Microsoft DoubleSpace disk compression utility program. Stac successfully sued Microsoft for patent infringement regarding the compression algorithm used in DoubleSpace. This resulted in the 1994 release of MS-DOS 6.21, which had the disk compression software removed. Shortly afterwards, version 6.22 was released, with a new disk compression system, DriveSpace, which had a different compression algorithm to avoid them infringing on competitors code. Prior to 1995, Microsoft licensed MS-DOS (and Windows) to computer manufacturers under three types of agreement: per-processor (a fee for each system the company sold), per-system (a fee for each system of a particular model), or per-copy (a fee for each copy of MS-DOS installed). The largest manufacturers used the per-processor arrangement, which had the lowest fee. This arrangement made it expensive for the large manufacturers to migrate to any other operating system, such as DR-DOS, in a classic case of vendor lock-down. In 1991, the US government's Federal Trade Commission began investigating Microsoft's licensing procedures resulting in a 1994 settlement agreement limiting Microsoft to per-copy licensing. Digital Research did not gain by this settlement, and years later its successor in interest Caldera (formerley SCO Group) sued Microsoft for damages. This lawsuit was settled with a monetary payment of US$150 million. Microsoft also used a variety of tactics in MS-DOS and several of their applications and development tools that, while operating perfectly when running on genuine MS-DOS (and PC-DOS), would break when run on another vendor's implementation of DOS. Notable examples of this practice included: * Microsoft QuickC v2.5, a.k.a. Programmer's Workbench and Microsoft C v6.0, modified the program's Program Segment Prefix using undocumented DOS functions, and then checked whether or not the associated value changed in a fixed position within the DOS data segment (also undocumented). * The (once infamous) AARD code, a block of code in the Windows 3.1 beta installer. It was XOR encrypted, self-modifying, and deliberately obfuscated, using various undocumented DOS structures and functions to determine whether or not Windows really was running on MS-DOS. * Interrupt routines called by Windows to inform MS-DOS that Windows is starting/exiting, information that MS-DOS retained in an IN_WINDOWS flag, in spite of the fact that MS-DOS and Windows were supposed to be two separate products. Windows NT 4.0 :Main article: Windows NT 4.0 Windows NT 4.0, although not based on DOS, provides a command-line interface similar to MS-DOS's character-mode interface. This command line is provided by a native executable, CMD.EXE. Many command-line applications (known as console applications) for Windows are incorrectly referred to as DOS applications, when actually they are full Windows applications which use the console for their output rather than a graphical interface, and cannot be run under any version of MS-DOS. Windows NT can run MS-DOS programs through the use of the NTVDM (NT Virtual DOS Machine), and the 16-bit COMMAND.COM interpreter from MS-DOS 5.0 is still included to maintain application compatibility with programs that expect it (This is illustrated by the output produced by the command "COMMMAND.COM /k ver", which displays "MS-DOS Version 5.00.500" in the console window). The command "ver" returns the string "Microsoft® Windows DOS" when executed under COMMMAND.COM, but "Microsoft Windows XP 5.1.2600" (or similar depending on the version of NT) when run from CMD.EXE. Recent versions of NT for x64 architectures, including Windows XP Professional x64 Edition, Windows Server 2003 x64 and Windows Vista x64, no longer include the NTVDM and can therefore no longer natively run MS-DOS (or 16-bit Windows) applications. For MS-DOS and Windows 3.11 or earlier programs, however, there exist alternatives in the form of emulators or virtual machines, such as Microsoft's own Virtual PC, Oracle VirtualBox VMWare, Bochs, QEMU, DOSBox, etc. Legacy compatibility From 1983 onwards, various companies have worked on Graphical User Interfaces capable of running on PC hardware. With DOS being the dominant operating system several companies released alternate shells, e.g. Microsoft Word for DOS, XTree, and the Norton Shell. However, this required duplication of effort and did not provide much consistency in interface design (even between products from the same company). Later, in 1985, Microsoft Windows was released as Microsoft's first attempt at providing a consistent user interface (for applications). The early versions of Windows ran on top of MS-DOS and its clones. At first Windows met with little success, but this was also true for most other companies' efforts as well, for example Graphical Environment Manager. After version 3.0 (1990), Windows gained marked acceptance. Later versions (Windows 95, Windows 98 and Windows Me) used the DOS boot process to launch itself into protected mode. Basic features related to the file system, such as long file names, were only available to DOS when running as a subsystem of Windows. Windows NT 4.0 ran independently of DOS, but included a DOS subsystem so applications could run in a virtual machine under the new operating system. With the latest Windows releases, even dual-booting MS-DOS is problematic as DOS may not be able to read the basic file system. Related systems Several similar products were produced by other companies. In the case of PC-DOS and DR-DOS, it is common but incorrect to call these "clones". Given that Microsoft manufactured PC-DOS for IBM, PC-DOS and MS-DOS were (to continue the genetic analogy) "identical twins" that diverged only in adulthood and eventually became quite different products; DR-DOS was a clone of itself once removed. * PC-DOS * DR-DOS * Novell DOS * OpenDOS * FreeDOS * FreeDOS 32 * GNU/DOS * PTS-DOS * DOSBox, a popular MS-DOS emulator These products are collectively referred to as DOS. However, MS-DOS can be a generic reference to DOS on IBM PC-compatible computers. See also * Comparison of x86 DOS operating systems - Comparison of MS-DOS and DOS-compatible operating systems * List of Microsoft Windows versions * List of DOS commands * Microsoft Windows * History of Microsoft Windows * Bad command or file name * DOSKey, an MS-DOS utility * Win32 console - a text-rendering system akin to MS-DOS